SYDNEY (Reuters) - Papua New Guinea began dismantling a shuttered Australian-run immigration detention centre on Thursday and warned it will use force if necessary to evict nearly 600 men if they refuse to leave within two days, according to a notice posted at the camp.

Asylum seekers protest on Manus Island, Papua New Guinea, in this picture taken from social media November 6, 2017. Social Media/Handout via REUTERS

The asylum seekers have barricaded themselves inside the Manus island centre for the past nine days, defying attempts by Australia and Papua New Guinea to close the camp in a standoff the United Nations describes as a “looming humanitarian crisis”.

The men fear violent reprisals from the Manus island community if they move from the camp to three transit centres, pending possible resettlement to the United States. The camp was closed on Oct. 31 and water and power have been cut off.

“You may become very sick under these conditions of overflowing sewerage, heaps of rubbish, no clean running water, no electricity and no food,” Papua New Guinea’s Immigration and Citizenship Service Authority said in a two-page notice reviewed by Reuters.

“You are therefore instructed to vacate this compound immediately...if necessary, force may be used to relocate those who refuse to move voluntarily for your own sake.”

The men inside the camp, who include asylum seekers from Afghanistan, Iran, Myanmar, Pakistan, Sri Lanka, and Syria, said they will continue to defy attempts to shut the camp.

They said they had exhausted their food supplies and were relying on rainwater to drink. Several of the men told Reuters that nearly 100 of them had fallen sick.

The notice added that demolition of fences would begin on Thursday. Behrouz Boochani, a Kurdish journalist from Iran who has been detained on Manus island for more than four years, said on Twitter that workers had begun that task.

“The refugees are watching them fearfully...(they) are extremely scared by immigration threat but still saying we will not leave this prison camp for another prison camp,” he said.

“Using force against ppl who’ve been suffering nearly 5yrs is no solution. If you’re going to solve this problem send us to safe third country.”

Australia has used the Manus island centre, and another on the tiny Pacific island of Nauru, to detain asylum seekers who try to reach its shores by boat. It says boat arrivals will never enter Australia, even if they are found to be refugees, as this would encourage people smugglers in Asia.

Papua New Guinea’s High Court ruled last year that the Manus centre, first opened in 2001, was illegal and the camp closed on Oct. 31, when Australian-funded security staff withdrew.

Thursday’s PNG government notice said the camp will soon revert to the control of the nation’s military and anyone there unlawfully will be liable for arrest. Papua New Guinea Prime Minister Peter O‘Neill on Wednesday said “appropriate means” would be used to apprehend those responsible for “disruption”.

Australia’s Immigration Minister Peter Dutton said on Thursday that the situation was “unacceptable...but the government won’t be backing down”.

The PNG Supreme Court rejected an application by one of the men to restore services on Tuesday, despite pleas from the United Nations to make food, water, medical supplies and power available. Lawyers for the asylum seekers are due to lodge an appeal against later on Thursday.